Method for transmitting control information in wireless communication system and apparatus therefor

ABSTRACT

A method of generating Acknowledgement/Negative Acknowledgement (ACK/NACK) information by a user equipment (UE) in a wireless communication system is discussed. The method includes receiving, by the UE from a base station (BS), a plurality of codewords through a plurality of downlink frequency bands related to a plurality of downlink carriers, wherein the UE is configured with a 1-codeword mode or a 2-codeword mode for each of the plurality of downlink frequency bands independently, and wherein a number of supported codewords is one for the 1-codeword mode or two for the 2-codeword mode; determining, by the UE, a total number of ACK/NACK bits, wherein the total number of ACK/NACK bits is determined based on a total number of the plurality of downlink carriers and the number of supported codewords; and generating, by the UE, a sequence of the ACK/NACK bits based on the total number of the ACK/NACK bits.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/708,225, filed on Dec. 9, 2019, now allowed, which is a continuationof U.S. application Ser. No. 16/239,168, filed on Jan. 3, 2019, now U.S.Pat. No. 10,505,693, which is a continuation of U.S. patent applicationSer. No. 16/049,270, filed on Jul. 30, 2018, now U.S. Pat. No.10,211,963, which is a continuation of U.S. patent application Ser. No.15/658,979, filed on Jul. 25, 2017, now U.S. Pat. No. 10,063,360, whichis a continuation of U.S. patent application Ser. No. 15/357,485, filedon Nov. 21, 2016, now U.S. Pat. No. 9,742,545, which is a continuationof U.S. patent application Ser. No. 14/553,837, filed on Nov. 25, 2014,now U.S. Pat. No. 9,525,518, which is a continuation of U.S. patentapplication Ser. No. 13/254,323, filed on Sep. 1, 2011, now U.S. Pat.No. 9,401,779, which is the National Phase of PCT InternationalApplication No. PCT/KR2010/001810 filed on Mar. 24, 2010, which claimsthe priority benefit under 35 U.S.C. § 119(e) to U.S. ProvisionalApplication Nos. 61/177,286 filed on May 12, 2009, 61/172,201 filed onApr. 23, 2009 and 61/164,461 filed on Mar. 29, 2009, all of which arehereby expressly incorporated by reference into the present application.

BACKGROUND OF THE INVENTION

A 3^(rd) generation partnership project long term evolution (3GPP LTE)communication system which is an example of a mobile communicationsystem to which the present invention can be applied will be describedin brief.

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a mobile communication system. The E-UMTS is an evolved version ofthe conventional UMTS system, and its basic standardization is inprogress under the 3rd Generation Partnership Project (3GPP). The E-UMTSmay also be referred to as a Long Term Evolution (LTE) system. Fordetails of the technical specifications of the UMTS and E-UMTS, refer toRelease 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1 , the E-UMTS includes a User Equipment (UE) 120,base stations (eNode B and eNB) 110 a and 110 b, and an Access Gateway(AG) which is located at an end of a network (E-UTRAN) and connected toan external network. Generally, the base stations can simultaneouslytransmit multiple data streams for a broadcast service, a multicastservice and/or a unicast service.

One or more cells may exist for one base station. One cell is set to oneof bandwidths of 1.25, 2.5, 5, 10, and 20 Mhz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to notify the user equipment oftime and frequency domains to which data will be transmitted andinformation related to encoding, data size, hybrid automatic repeat andrequest (HARQ). Also, the base station transmits uplink (UL) schedulinginformation of uplink data to the corresponding user equipment to notifythe user equipment of time and frequency domains that can be used by thecorresponding user equipment, and information related to encoding, datasize, HARQ. An interface for transmitting user traffic or controltraffic can be used between the base stations. A Core Network (CN) mayinclude the AG and a network node or the like for user registration ofthe UE. The ΔG manages mobility of a UE on a Tracking Area (TA) basis,wherein one TA includes a plurality of cells.

Although the wireless communication technology developed based on WCDMAhas been evolved into LTE, request and expectation of users andproviders have continued to increase. Also, since another wirelessaccess technology is being continuously developed, new evolution of thewireless communication technology is required for competitiveness in thefuture. In this respect, reduction of cost per bit, increase ofavailable service, adaptable use of frequency band, simple structure,open type interface, proper power consumption of user equipment, etc.are required.

Recently, standardization of advanced technology of LTE is in progressunder the 3rd Generation Partnership Project (3GPP). This technologywill be referred to as “LTE-Advanced” or “LTE-A.” One of importantdifferences between the LTE system and the LTE-A system is difference insystem bandwidth. The LTE-A system aims to support a wideband of maximum100 MHz. To this end, the LTE-A system uses carrier aggregation orbandwidth aggregation that achieves a wideband using a plurality ofcomponent carriers. Carrier aggregation allows a plurality of componentcarriers to be used as one logical frequency band, whereby a widerfrequency band is used. A bandwidth of each component carrier can bedefined based on a bandwidth of a system block used in the LTE system.

SUMMARY OF THE INVENTION

The present invention relates to a method for transmitting a controlsignal in a wireless communication system, and more particularly, to amethod for transmitting ACK/NACK signal from a user equipment in awireless communication system to which carrier aggregation is applied.

Accordingly, the present invention is directed to a method fortransmitting a control signal in a wireless communication system and anapparatus therefor, which substantially obviate one or more problems dueto limitations and disadvantages of the related art.

An object of the present invention is to provide a method and apparatusfor transmitting ACK/NACK signal in a wireless communication system towhich carrier aggregation is applied.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for transmitting ACK/NACK (Acknowledgement/Negative ACK) signalsin a wireless communication system comprises receiving a plurality ofdata blocks from a base station; generating ACK/NACK signalscorresponding to the plurality of data blocks; allocating resources fortransmitting the ACK/NACK signals, wherein the resources are allocatedindependently per slot; and transmitting the ACK/NACK signals throughone uplink component carrier by using the allocated resources. In thiscase, the plurality of data blocks are received at the same time througha plurality of downlink component carriers. Preferably, step ofreceiving a plurality of data blocks includes receiving two or more datablocks through at least one downlink component carrier among theplurality of downlink component carriers.

More preferably, the step of allocating resources includes allocatingthe resources to minimize the difference in the number of the ACK/NACKsignals transmitted per slot.

In another aspect of the present invention, a method for transmittingACK/NACK (Acknowledgement/Negative ACK) signals in a wirelesscommunication system comprises receiving a plurality of data blocksthrough a plurality of downlink component carriers from a base station;generating ACK/NACK signals corresponding to the plurality of datablocks; mapping the ACK/NACK signals into a bit index; allocatingcontrol channel resources for transmitting the bit index; andtransmitting the bit index through one uplink component carrier by usingthe allocated control channel resources. In this case, the controlchannel resources are payload of PUCCH (physical uplink control channel)format 2.

In still another aspect of the present invention, a method fortransmitting ACK/NACK (Acknowledgement/Negative ACK) signals in awireless communication system comprises receiving a plurality of datablocks through a plurality of downlink component carriers from a basestation; generating ACK/NACK signals corresponding to the plurality ofdata blocks; allocating containers for transmitting the ACK/NACK signalsin control channel resources in accordance with an index order of thedownlink component carriers as much as the received data blocks; andtransmitting the ACK/NACK signals through one uplink component carrierby using the allocated containers. Likewise, the control channelresources are preferably payload of PUCCH (physical uplink controlchannel) format 2.

More preferably, the step of receiving a plurality of data blocksincludes receiving two or more data blocks through at least one downlinkcomponent carrier among the plurality of downlink component carriers,and the step of allocating containers includes allocating the containersin accordance with the order of the data blocks received through the atleast one downlink component carrier.

Further still another aspect of the present invention, a user equipmentcomprises a receiving module receiving a plurality of data blocks from abase station; a processor generating ACK/NACK signals corresponding tothe plurality of data blocks and allocating resources for transmittingthe ACK/NACK signals, wherein the resources are allocated independentlyper slot; and a transmitting module transmitting the ACK/NACK signalsthrough one uplink component carrier by using the allocated resources.In this case, the receiving module receives the plurality of data blocksat the same time through a plurality of downlink component carriers.Preferably, the receiving module receives two or more data blocksthrough at least one downlink component carrier among the plurality ofdownlink component carriers.

More preferably, the processor allocates the resources to minimize thedifference in the number of the ACK/NACK signals transmitted per slot.

In further still another aspect of the present invention, a userequipment comprises a receiving module receiving a plurality of datablocks at the same time through a plurality of downlink componentcarriers from a base station; a processor generating ACK/NACK signalscorresponding to the plurality of data blocks, mapping the ACK/NACKsignals into a bit index, and allocating control channel resources fortransmitting the bit index; and a transmitting module transmitting thebit index through one uplink component carrier by using the allocatedcontrol channel resources. In this case, the control channel resourcesare preferably payload of PUCCH (physical uplink control channel) format2.

In further still another aspect of the present invention, a userequipment comprises a receiving module receiving a plurality of datablocks at the same time through a plurality of downlink componentcarriers from a base station; a processor generating ACK/NACK signalscorresponding to the plurality of data blocks and allocating containersfor transmitting the ACK/NACK signals in control channel resources inaccordance with an index order of the downlink component carriers asmuch as the received data blocks; and a transmitting module transmittingthe ACK/NACK signals through one uplink component carrier by using theallocated containers. Likewise, the control channel resources arepreferably payload of PUCCH (physical uplink control channel) format 2.

More preferably, the receiving module receives a plurality of datablocks includes receiving two or more data blocks through at least onedownlink component carrier among the plurality of downlink componentcarriers, and the processor allocates the containers in accordance withthe order of the data blocks received through the at least one downlinkcomponent carrier.

According to the embodiments of the present invention, ACK/NACK signalscan be transmitted efficiently in the wireless communication system towhich carrier aggregation is applied.

It is to be understood that the advantages that can be obtained by thepresent invention are not limited to the aforementioned advantages andother advantages which are not mentioned will be apparent from thefollowing description to the person with an ordinary skill in the art towhich the present invention pertains.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a mobile communication system;

FIG. 2 is a diagram illustrating a transmitter and a receiver for OFDMAand SC-FDMA;

FIG. 3 is a diagram illustrating a structure of a radio frame used in anLTE system;

FIG. 4 is a diagram illustrating a structure of a downlink radio frameused in an LTE system;

FIG. 5 is a diagram illustrating a structure of an uplink subframe usedin an LTE system;

FIG. 6 is a diagram illustrating a structure of a PUCCH for ACK/NACKtransmission in an LTE system;

FIG. 7 is a diagram illustrating an example of determining PUCCHresources for ACK/NACK signal transmission;

FIG. 8 is a diagram illustrating an example of communication performedunder multiple component carriers;

FIG. 9 is a diagram illustrating a PUCCH Format 1 extension schemeaccording to one embodiment of the present invention;

FIG. 10 , including views (a) and (b), is a diagram illustrating a PUCCHFormat 2 extension scheme according to one embodiment of the presentinvention;

FIG. 11 , including views (a) and (b), is a diagram illustrating a PUCCHFormat 2 extension scheme according to another embodiment of the presentinvention;

FIG. 12 is a diagram illustrating a method for allocating a plurality ofACK/NACK information to payload of PUCCH format 2 in accordance with oneembodiment of the present invention;

FIG. 13 is a diagram illustrating a method for allocating a plurality ofACK/NACK/DTX information to payload of PUCCH format 2 in accordance withone embodiment of the present invention;

FIG. 14 is a diagram illustrating a method for transmitting ACK/NACK/DTXinformation in accordance with one embodiment of the present inventionwhen a base station is operated in a MIMO mode and the number ofdownlink component carriers is less than 4;

FIG. 15 is a diagram illustrating a method for transmitting ACK/NACK/DTXinformation in accordance with one embodiment of the present inventionwhen a base station is operated in a MIMO mode and the number ofdownlink component carriers is more than 5;

FIG. 16 is a diagram illustrating a case where component carriers 1 and3 are operated in a Non-MIMO mode and the other component carriers areoperated in a MIMO mode;

FIG. 17 is a diagram illustrating a method for allocating PUCCH format 2dedicated resources according to one embodiment of the presentinvention;

FIG. 18 is a diagram illustrating an example of using PUCCH format 2dedicated resources allocated as resources for LTE-A in accordance withone embodiment of the present invention;

FIG. 19 is a diagram illustrating another method for transmittingACK/NACK information in accordance with one embodiment of the presentinvention;

FIG. 20 is a diagram illustrating an example of transmitting ACK/NACKinformation according to one embodiment of the present invention in caseof normal CP;

FIG. 21 is a diagram illustrating an example of transmitting ACK/NACKinformation according to one embodiment of the present invention in caseof extended CP;

FIG. 22 is a diagram illustrating a case where ACK/NACK information of aspecific downlink component carrier is repeated; and

FIG. 23 is a diagram illustrating a base station and a user equipmentthat can be applied to the embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, structures, operations, and other features of the presentinvention will be understood readily by the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to 3GPP system.

Hereinafter, a system that includes a system band of a single componentcarrier will be referred to as a legacy system or a narrowband system.By contrast, a system that includes a system band of a plurality ofcomponent carriers and uses at least one or more component carriers as asystem block of a legacy system will be referred to as an evolved systemor a wideband system. The component carrier used as a legacy systemblock has the same size as that of the system block of the legacysystem. On the other hand, there is no limitation in sizes of the othercomponent carriers. However, for system simplification, the sizes of theother component carriers may be determined based on the size of thesystem block of the legacy system. For example, the 3GPP LTE (Release-8)system and the 3GPP LTE-A (Release-9) system are evolved from the legacysystem.

Based on the aforementioned definition, the 3GPP LTE (Release-8) systemwill herein be referred to as an LTE system or the legacy system. Also,a user equipment that supports the LTE system will be referred to as anLTE user equipment or a legacy user equipment. The 3GPP LTE-A(Release-9) system will be referred to as an LTE-A system or an evolvedsystem. Also, a user equipment that supports the LTE-A system will bereferred to as an LTE-A user equipment or an evolved user equipment.

For convenience, although the embodiment of the present invention willbe described based on the LTE system and the LTE-A system, the LTEsystem and the LTE-A system are only exemplary and can be applied to allcommunication systems corresponding to the aforementioned definition.

FIG. 2 is a block diagram illustrating a transmitter and a receiver forOFDMA and SC-FDMA. In an uplink, a transmitter 202˜214 may be a part ofa user equipment, and a receiver 216˜230 may be a part of a basestation. In a downlink, a transmitter may be a part of a base station,and a receiver may be a part of a user equipment.

Referring to FIG. 2 , an OFDMA transmitter includes a serial to parallelconverter 202, a sub-carrier mapping module 206, an M-point inversediscrete Fourier transform (IDFT) module 208, a cyclic prefix (CP)addition module 210, a parallel to serial converter 212, and a radiofrequency (RF)/digital to analog converter (DAC) module 214.

A signal processing procedure in the OFDMA transmitter will be describedbelow. First of all, bit streams are modulated to data symbol sequences.The bit streams can be obtained by performing various signal processes,such as channel encoding, interleaving and scrambling, for a data blocktransferred from a medium access control (MAC) layer. The bit streamsmay be designated as codewords, and are equivalent to the data blocktransferred from the MAC layer. The data block transferred from the MAClayer may be designated as a transport block. Examples of a modulationscheme include, but not limited to, BPSK (binary phase shift keying),QPSK (quadrature phase shift keying), and n-QAM (quadrature amplitudemodulation). Afterwards, the data symbol sequences in series areconverted to parallel data symbol sequences as much as N (202). N numberof data symbols are mapped with N number of subcarriers allocated amonga total of M number of subcarriers, and the other M-N number of carriersare padded with 0 (206). The data symbols mapped in a frequency domainare converted to time domain sequences through M-point IDFT processing(208). Afterwards, in order to reduce inter-symbol interference (ISI)and inter-carrier interference (ICI), cyclic prefix is added to the timedomain sequences to generate OFDMA symbols (210). The generated OFDMAsymbols are converted from parallel symbols to serial symbols (212).Then, the OFDMA symbols are transmitted to the receiver throughdigital-to-analog conversion and frequency uplink conversion (214).Other user is allocated with available subcarriers among the remainingM-N number of subcarriers. On the other hand, the OFDMA receiverincludes an RF/ADC (analog to digital converter) module 216, aserial-to-parallel converter 218, a cyclic prefix (CP) removing module220, an M-point discrete Fourier transform (DFT) module 224, asubcarrier demapping/equalization module 226, a parallel-to-digitalconverter 228, and a detection module 230. A signal processing procedureof the OFDMA receiver will be configured in reverse order of the OFDMAtransmitter.

As compared with the OFDMA transmitter, the SC-FDMA transmitteradditionally includes an N-point DFT module 204 prior to the subcarriermapping module 206. The SC-FDMA transmitter can reduce a peak-to-averagepower ratio (PAPR) of a transmitting signal more remarkably than theOFDMA transmitter by spreading a plurality of data to the frequencydomain through DFT prior IDFT processing. Also, as compared with theOFDMA receiver, the SC-FDMA receiver additionally includes an N-pointIDFT module 228 after the subcarrier demapping module 226. A signalprocessing procedure of the SC-FDMA receiver will be configured inreverse order of the SC-FDMA transmitter.

FIG. 3 is a diagram illustrating a structure of a radio frame used inthe LTE system.

Referring to FIG. 3 , the radio frame has a length of 10 ms(327200·T_(s)) and includes 10 subframes of an equal size. Each subframe has a length of 1 ms and includes two slots. Each slot has alength of 0.5 ms (15360·T_(s)). In this case, T_(s) represents asampling time, and is expressed by T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸(about 33 ns). The slot includes a plurality of OFDMA (or SC-FDMA)symbols in a time domain, and includes a plurality of resource blocks(RBs) in a frequency domain. In the LTE system, one resource blockincludes twelve (12) subcarriers×seven (or six) OFDMA (or SC-FDMA)symbols. A transmission time interval (TTI) which is a transmission unittime of data can be determined in a unit of one or more subframes. Theaforementioned structure of the radio frame is only exemplary, andvarious modifications can be made in the number of subframes included inthe radio frame or the number of slots included in the subframe, or thenumber of OFDMA (or SC-FDMA) symbols included in the slot.

FIG. 4 is a diagram illustrating an example of communication performedunder a single component carrier status. FIG. 4 corresponds to acommunication example of the LTE system. In a frequency division duplex(FDD) mode, data transmission and reception is performed through onedownlink band and one uplink band corresponding to the downlink band. Inmore detail, in the FDD mode, the radio frame structure of FIG. 3 isused for downlink transmission or uplink transmission only. On the otherhand, in a time division duplex (TDD) mode, the same frequency band isdivided into a downlink interval and an uplink interval corresponding tothe downlink interval in the time domain. In more detail, in the TDDmode, the radio frame structure of FIG. 3 is divided for downlinktransmission and uplink transmission corresponding to the downlinktransmission.

A method for performing HARQ (Hybrid Automatic Repeat and request) in auser equipment will be described with reference to FIG. 4 . In the LTEsystem, control information (for example, scheduling information) ofdownlink data transmission of the base station is transferred to theuser equipment through a downlink control channel established within acontrol region of a downlink subframe. The downlink control channelincludes a physical downlink control channel (PDCCH). The user equipmentcan receive scheduled data through a downlink common channel indicatedby scheduling information (for example, resources allocated with data,size of data, coding mode, redundancy version, etc.) after receiving thescheduling information through the control channel. The downlink commonchannel includes a physical uplink channel (PDSCH). Afterwards, the userequipment can transmit acknowledgement information (for example, HARQACK/NACK) in response to downlink data to the base station through theuplink control channel established within the control region of theuplink subframe. The uplink control channel includes a physical uplinkcontrol channel (PUCCH). For convenience, HARQ ACK/NACK will simply beexpressed as ACK/NACK signal. The base station performs HARQ fordownlink data indicated as NACK after receiving the ACK/NACK signal. Ifthe base station transmits a plurality of downlink data to the userequipment, the HARQ process can be performed for each transport blockcorresponding to each of the downlink data.

FIG. 5 is a diagram illustrating a structure of an uplink subframe usedin an LTE system.

Referring to FIG. 5 , the uplink subframe includes a plurality of slots(for example, two slots). The slot can include a different number ofSC-FDMA symbols depending on a CP length. For example, in case of anormal CP, the slot includes seven SC-FDMA symbols. The uplink subframeis divided into a data region and a control region. The data regionincludes a physical uplink shared channel (PUSCH), and is used totransmit a data signal such as voice. The control region includes aphysical uplink control channel (PUCCH), and is used to transmit controlinformation. The PUCCH includes a pair of resource blocks (RBs) (forexample, m=0,1,2,3) located at both ends of the data region on thefrequency axis, and is hopped using the slot as a boundary. The controlinformation includes HARQ ACK/NACK, channel quality indicator (CQI),precoding matrix index (PMI), and rank index (RI). Also, the PUSCH andthe PUCCH are not transmitted at the same time. The following Table 1illustrates features PUCCH Format described in 3GPP TS 36.211 Release-8.

TABLE 1 PUCCH Modulation Number of bits per format scheme subframe,M_(bit) 1  N/A N/A 1a BPSK 1 1b QPSK 2 2  QPSK 20 2a QPSK + BPSK 21 2bQPSK + QPSK 22

FIG. 6 is a diagram illustrating a structure of a physical uplinkcontrol channel (PUCCH) for transmitting ACK/NACK.

Referring to FIG. 6 , in case of a normal cyclic prefix (CP), areference signal (UL RS) is carried in three continuous symbols locatedin the center of the slot, and control information (i.e., ACK/NACKsignals) is carried in the other four symbols. In case of an extendedCP, the slot includes six symbols, wherein a reference signal is carriedin the third and fourth symbols. ACK/NACK signals from a plurality ofuser equipments are multiplexed with one PUCCH resource by using a CDMmode. The CDM mode is implemented using (quasi) orthogonal spreadingcodes for cyclic shift (CS) and/or time spreading of sequences forfrequency spreading. For example, the ACK/NACK signals are identifiedusing different cyclic shifts (CS) (frequency spreading) of computergenerated constant amplitude zero auto correlation (CG-CAZAC) sequenceand/or different Walsh/DFT orthogonal codes (time spreading). w0, w1,w2, w3 multiplied after IFFT obtain the same result even though they aremultiplied before IFFT. In the LTE system, PUCCH resources fortransmitting ACK/NACK are expressed by combination of (quasi)orthogonalcodes for time spreading, location of frequency-time resources (forexample, resource block), and cyclic shift of sequences for frequencyspreading. Each PUCCH resource is indicated using a PUCCH (resource)index.

FIG. 7 is a diagram illustrating an example of determining PUCCHresources for ACK/NACK signal transmission. In the LTE system, PUCCHresources for ACK/NACK are not previously allocated to each userequipment but used by a plurality of user equipments within a cell pertiming point. In more detail, the PUCCH resources used for ACK/NACKtransmission correspond to PDCCH carrying scheduling information ofcorresponding downlink data. In each downlink subframe, an entire regionwhere PDCCH is transmitted includes a plurality of control channelelements (CCEs), and the PDCCH transmitted to the user equipmentincludes one or more CCEs. The user equipment transmits ACK/NACK througha PUCCH resource corresponding to a specific CCE (for example, firstCCE) among CCEs constituting PDCCH received therein.

Referring to FIG. 7 , each square block in a downlink component carrier(DL CC) represents a CCE, and each square block in an uplink componentcarrier (UL CC) represents a PUCCH resource. Each PUCCH indexcorresponds to a PUCCH resource for ACK/NACK. It is assumed that PDSCHinformation is transferred through a PDCCH that includes CCEs Nos. 4 to6 as illustrated in FIG. 7 . In this case, the user equipment transmitsACK/NACK through PUCCH No. 4 corresponding to CCE No. 4 which is thefirst CCE of the PDCCH. FIG. 6 illustrates that maximum M number ofPUCCHs exist in the UL CC when maximum N number of CCEs exist in the DLCC. Although N may be equal to M (N=M), M may be different from N, andmapping between CCEs and PUCCHs may be overlapped.

In more detail, in the LTE system, PUCCH resource index is defined asfollows.n ⁽¹⁾ _(PUCCH) =n _(CCE) +N ⁽¹⁾ _(PUCCH)  [Equation 1]

In this case, n⁽¹⁾ _(PUCCH) represents a PUCCH resource index fortransmitting ACK/NACK, N⁽¹⁾ _(PUCCH) represents a signaling valuetransferred from an upper layer, and n_(CCE) represents the smallestvalue of CCE indexes used for PDCCH transmission.

FIG. 8 is a diagram illustrating an example of communication performedunder multiple component carriers. FIG. 8 corresponds to a communicationexample of the LTE-A system. The LTE-A system uses carrier aggregationor bandwidth aggregation where a plurality of uplink/downlink frequencyblocks are collected to use broader frequency bandwidths, thereby usinggreater uplink/downlink bandwidths. Each frequency block is transmittedusing a component carrier (CC).

Referring to FIG. 8 , five component carriers (CCs) of 20 MHz arecollected in the uplink/downlink to support a bandwidth of 100 MHz. Therespective CCs may adjoin each other in the frequency domain or not. Theradio frame structure illustrated in FIG. 3 can be applied even in thecase that multiple component carriers are used. However, since radioframe, subframe and slot are defined in a time unit, the base stationand the user equipment can transmit and receive a signal through aplurality of component carriers on one subframe. FIG. 8 illustrates thata bandwidth of each UL CC is the same as and symmetrical to that of eachDL CC. However, the bandwidths of the respective component carriers maybe defined independently. For example, the bandwidths of the UL CCs maybe configured as 5 MHz (UL CC0)+20 MHz (UL CC1)+20 MHz (UL CC2)+20 MHz(UL CC3)+5 MHz (UL CC4). Also, asymmetrical carrier aggregation wherethe number of uplink component carriers is different from the number ofdownlink component carriers may be configured. The asymmetrical carrieraggregation may occur due to a limit of available frequency bandwidth,or may be configured artificially by network establishment. Also,although an uplink signal and a downlink signal are transmitted throughCCs mapped with each other one to one, CC through which a signal isactually transmitted may be varied depending on network establishment orsignal type. For example, CC through which scheduling command istransmitted may be different from CC through which data are transmittedin accordance with scheduling command. Also, uplink/downlink controlinformation can be transmitted through a specific UL/DL CC regardless ofmapping between CCs.

If the number of UL CCs is, but not limited to, smaller than the numberof DL CCs, the user equipment should transmit ACK/NACK for transmissionof a plurality of downlink PDSCHs through smaller uplink PUCCHs. Inparticular, it may be set in such a manner that ACK/NACK fortransmission of a plurality of downlink PDSCHs is transmitted through aspecific UL CC only. Also, if the number of UL CCs is the same as thenumber of DL CCs and the user equipment uses MIMO (Multiple InputMultiple Output) or is operated in accordance with the TDD mode, theuser equipment receives a plurality of transport blocks. In this case,the user equipment should transmit ACK/NACK signals for a plurality ofdata units through the limited PUCCH resource.

Meanwhile, in the LTE system according to the related art, PUCCHresources are repeated within a subframe in a slot unit, and ACK/NACKsignals having the same value are transmitted through each slot.Repetition of the PUCCH resources defined in the LTE system is toenhance reliability of ACK/NACK signals through time/frequencydiversity. However, information of ACK/NACK signals that can betransmitted at once is reduced in proportion to the number of repetitiontimes of the PUCCH resources.

Hereinafter, the present invention suggests that ACK/NACK signals aretransmitted efficiently to correspond to transport blocks receivedthrough a plurality of component carriers in the LTE-A system to whichcarrier aggregation is applied. Also, in the present invention, it isassumed that ACK/NACK signals corresponding to transport blocks receivedthrough a plurality of downlink component carriers are transmittedthrough one uplink component carrier.

<Extension of PUCCH Format 1>

Generally, in PUCCH Format 1 system, the maximum number of ACK/NACKsignals that can be transmitted is determined depending on modulationorder. For example, one ACK/NACK signal can be transmitted in case ofBPSK while two ACK/NACK signals can be transmitted in case of QPSK.Hereinafter, a method for transmitting ACK/NACK signals for transportblocks transmitted through a plurality of component carriers byextending the PUCCH Format 1 shown in Table 1 will be described.

FIG. 9 is a diagram illustrating a PUCCH Format 1 extension schemeaccording to one embodiment of the present invention.

Referring to FIG. 9 , in the present invention, PUCCH resources areallocated to ACK/NACK signals per slot to. This will be referred to asslot division. According to the slot division, PUCCH resources repeatedper slot within a subframe can be used independently during ACK/NACKsignal transmission. In other words, the PUCCH resources repeated perslot within a subframe are subjected to decoupling during ACK/NACKsignal transmission. Accordingly, the PUCCH resources for transmittingthe ACK/NACK signals can be selected independently based on the slot.

Also, modulation order may be set per slot to flexibly control thenumber of ACK/NACK signals that can be transmitted through one slot. Thefollowing Table 2 illustrates an example of a PUCCH Format 1 extensionscheme according to the number of downlink component carriers if thebase station is not operated in a MIMO mode, i.e., if only one transportblock is received through one downlink component carrier.

TABLE 2 ACK/NACK count; x = # of A/Ns Single Tx/ SM with n Diversityresources PUCCH format 1 Ceil{x/n} <= 1 Rel-8 PUCCH 2 Ceil{x/n} <= 2Rel-8 PUCCH 3 Ceil{x/n} <= 3 Slot division with one of two slots havingQPSK 4 Ceil{x/n} <= 4 Slot division with two slots having QPSK 5Ceil{x/n} <= 5 Slot division with one of two slots having 8PSK

In Table 2, Ceil{x/n} means a rounded off value of x/n, x means a totalnumber of ACK/NACK signals to be transmitted, and n means the number ofPUCCH resources that can be allocated for independent ACK/NACK signaltransmission.

Meanwhile, if the base station can transmit ACK/NACK signals to twotransport blocks through one component carrier as the MIMO mode isapplied to the base station, the scheme of Table 2 is needed to becorrected. The following Table 3 illustrates a corrected example of theTable 2.

TABLE 3 ACK/NACK count; x = # of A/Ns Single Tx/ SM with n Diversityresources PUCCH format ~2 Ceil{x/n} <= 2 Rel-8 PUCCH ~4 Ceil{x/n} <= 4Slot division with two slots having QPSK ~6 Ceil{x/n} <= 6 Slot divisionwith two slots having 8PSK ~8 Ceil{x/n} <= 8 A. Slot division with twoslots having 16 QAM(or PSK) B. Bundling can be used among spatial domainor carrier domain; Limit the modulation order to 8PSK or QPSK with slotdivision ~10 Ceil{x/n} <= 10 A. Slot division with two slots having 32QAM(or PSK) B. Slot division with one of two slots having 64QAM C.Bundling can be used among spatial domain or carrier domain; Limit themodulation order to 8PSK or QPSK with slot division

As illustrated in Table 3, the number of ACK/NACK signals transmittedper slot is uniformly maintained or its difference is minimized, wherebymodulation order used in each slot is set at a low level as low aspossible.

As another PUCCH Format 1 extension scheme, it is set in such a mannerthat hopping between slots is not performed. For example, it means thatPUCCH A1 and PUCCH B3 of FIG. 5 are used as one PUCCH resource.According to the PUCCH Format 1 extension scheme, as same resource blockis used as the PUCCH resource, channel response is not varied rapidly inthe frequency domain. In this case, a separate modulation scheme may beapplied to each slot, whereby additional ACK/NACK signals can bedefined. Namely, different modulation schemes can be applied to areference signal (DM-RS) part of the first slot and a reference signal(DM-RS) part of the second slot, and separately from ACK/NACK messagetransmitted to each slot, another ACK/NACK message can be transmitted tothe reference symbol.

Also, as another method in addition to the slot division scheme, theresource used by the first message or the second message of FIG. 9 issubdivided based on the PUCCH DM-RS applied to each slot, wherebyindependent message can be transmitted. At this time, a length of acover sequence in the time domain can be reduced to half.

<Extension of PUCCH Format 2>

As an example of a method for transmitting ACK/NACK information usingPUCCH format 2 system, there may be considered a method for mappingACK/NACK information for each transport block into OFDM symbol withoutspreading of a time domain after performing coding and modulation forthe ACK/NACK information. Also, there may be considered a method fortransmitting a plurality of ACK/NACK information to payload of PUCCHformat 2. Hereinafter, the above two methods will be described indetail.

First of all, the first method will be described. FIG. 10 , includingviews (a) and (b), is a diagram illustrating a PUCCH Format 1 extensionscheme according to one embodiment of the present invention. Inparticular, it is noted that (a) of FIG. 10 illustrates that normal CPis applied while (b) of FIG. 10 illustrates that extended CP is applied.

Referring to FIG. 10 , four messages are used as resources that cantransmit maximum two kinds of ACK/NACK information as QPSK is applied.Particularly, in (a) of FIG. 10 , symbol S4 can be used if the firstmessage and the third message are transmitted or if the second messageand the fourth message are transmitted. If the messages are transmittedusing three symbols, detection throughput is improved. The symbols canbe used for modulation scheme of higher order or to set priority ofACK/NACK messages.

The following Table 4 illustrates an example of a PUCCH Format 2extension scheme if MIMO mode is not used.

TABLE 4 ACK/NACK count; x = # of A/Ns Single Tx/ SM with n Diversityresources PUCCH format 1 Ceil{x/n} <= 1 Rel-8 PUCCH format 1 2 Ceil{x/n}<= 2 Rel-8 PUCCH format 1 3 Ceil{x/n} <= 3 PUCCH format 2 extension: A.Two messages among four messages are the same ACK/NACK information. B.One message have QPSK and the other three message with BPSK 4 Ceil{x/n}<= 4 PUCCH format 2 extension: A. Each message have BPSK modulation withone ACK/NACK B. Message1 = Message2 and Message3 = Message4, where QPSKmodulation is used for each slot 5 Ceil{x/n} <= 5 PUCCH format 2extension: One of four messages has QPSK modulation and the others haveBPSK modulation for ACK/NACK transmission

The following Table 5 illustrates an example of a PUCCH Format 2extension scheme if MIMO mode is not used.

TABLE 5 ACK/NACK count; x = # of A/Ns Single Tx/ SM with n Diversityresources PUCCH format ~2 Ceil{x/n} <= 2 Rel-8 PUCCH ~4 Ceil{x/n} <= 4PUCCH format 2 extension: Each A/N can be located on each message withBPSK ~6 Ceil{x/n} <= 6 PUCCH format 2 extension: two messages can haveQPSK modulation and the other two message can have BPSK ~8 Ceil{x/n} <=8 PUCCH format 2 extension: Each A/N can be located on each message withQPSK ~10 Ceil{x/n} <= 10 PUCCH format 2 extension: two messages can have8PSK modulation and the other two message can have QPSK

FIG. 11 , including views (a) and (b), is a diagram illustrating a PUCCHFormat 2 extension scheme according to another embodiment of the presentinvention. In particular, in the PUCCH Format 2 extension scheme of FIG.11 , reference symbols are used.

Unlike the PUCCH Format 1 extension scheme in which reference symbolsare spread into the time domain using spreading sequence, in the PUCCHFormat 2 extension scheme, reference symbols are neither spread normodulated using any information except that CQI and ACK/NACK aretransmitted together or CIQ and SR are transmitted together.Accordingly, a different modulation scheme for each slot can be appliedto the reference symbols to message the fifth message, whereby ACK/NACKinformation is transmitted using the fifth message.

If the ACK/NACK information is transmitted using the fifth message, theTable 4 and the Table 5 can be simplified as illustrated in thefollowing Table 6 and Table 7.

TABLE 6 ACK/NACK count; x = # of A/Ns Single Tx/ SM with n Diversityresources PUCCH format 1 Ceil{x/n} <= 1 Rel-8 PUCCH format 1 2 Ceil{x/n}<= 2 Rel-8 PUCCH format 1 3 Ceil{x/n} <= 3 PUCCH format 2 extension:Message 5 is not used A. Two messages among four messages are the sameACK/NACK information. B. One message have QPSK and the other threemessage with BPSK 4 Ceil{x/n} <= 4 PUCCH format 2 extension: Message 5is not used A. Each message have BPSK modulation with one ACK/NACK B.Message1 = Message2 and Message3 = Message4, where QPSK modulation isused for each slot 5 Ceil{x/n} <= 5 PUCCH format 2 extension: Eachmessage have BPSK modulation

TABLE 7 ACK/NACK count; x = # of A/Ns Single Tx/ SM with n Diversityresources PUCCH format ~2 Ceil{x/n} <= 2 Rel-8 PUCCH ~4 Ceil{x/n} <= 4PUCCH format 2 extension: Message5 is not used, Each A/N can be locatedon four messages with BPSK ~6 Ceil{x/n} <= 6 PUCCH format 2 extension:Message5 is not used, two messages can have QPSK modulation and theother two message can have BPSK ~8 Ceil{x/n} <= 8 PUCCH format 2extension: Message5 is not used, Each A/N can be located on fourmessages with QPSK ~10 Ceil{x/n} <= 10 PUCCH format 2 extension: Fivemessages can have QPSK modulation

The method for transmitting separate ACK/NACK information through firstto fifth messages has been described as above. Hereinafter, a method fortransmitting a plurality of ACK/NACK information to payload of PUCCHformat 2 will be described.

Generally, PUCCH format 2 transmits 21 bits for CQI transmission, PUCCHformat 2a transmits 21 bits for CQI+A/N(1 bit) transmission, and PUCCHformat 2b transmits 22 bits for CQI+A/N(2 bits) transmission. This isbased on the number of coded bits which have been channel coded. Payloadsize of the PUCCH format 2 is 13 bits. Accordingly, if maximum payloadof 13 bits of the PUCCH format 2 is used, a plurality of ACK/NACKinformation can be transmitted.

It is assumed that frequency aggregation is used. In this case, ACK/NACKinformation of 1 bit is transmitted to correspond to transport blocksreceived through each downlink component carrier, the number of bits ofrequired ACK/NACK information is determined depending on the number oftransport blocks through one component carrier. When carrier aggregationis used, the number of bits of A/N required to transmit 1-bit UL A/N forTB transmission of each DL CC is as follows: (i) in case of single TB(non-MIMO case): 1-bit A/N is transmitted for each TB when a single TBis transmitted in each DL CC, and thus (1×Ncc) bits are required for A/Nbits (Ncc is the number of DL CCs), and (ii) in case of multiple TBs(MIMO case, SM): 1-bit A/N is transmitted for each TB when two TBs aretransmitted in each DL CC using SM, and thus (2×Ncc) bits are requiredfor A/N bits (Ncc is the number of DL CCs).

FIG. 12 is a diagram illustrating a method for allocating a plurality ofACK/NACK information to payload of PUCCH format 2 in accordance with oneembodiment of the present invention.

When a UE which uses carrier aggregation generates a payload in order totransmit multiple A/Ns using the PUCCH format 2, the UE can (i)sequentially generate A/N information for respective DL CCs, (ii)sequentially generate A/N information for respective TBs for respectiveDL CCs, or (iii) sequentially generate A/N information for respectiveTBs for respective DL CCs even when the respective DL CCs have differenttransmission modes (when non-MIMO and MIMO are differently used forCCs). Examples of generation of A/N information are shown in the FIG. 12.

In the example of the FIG. 12 , the bit position of A/N for CCs may befixed or varied depending on the number of active (monitored) CCs orscheduled CCs. In the case where the bit position is varied, it isrequired that there is no ambiguity in a total number of ACK/NACK thatneed to be transmitted among downlink CCs. If there is ambiguity, it isdesirable that the bit position is not changed. Furthermore, if carriersare transmitted in different transmission modes, the position may bevaried only when there is no problem in the transmission modes of thecarriers and PDCCH decoding, or when a DL CC that has been scheduled isclearly indicated. In consideration of a total number of bits that canbe transmitted is 13, the bit position can be determined by mapping thecarriers in advance in the above structure. For example, if a maximumnumber of TBs that can be transmitted using one DL CC, that is, amaximum number of required ACK/NACK, is two, two bits are allocated toeach DL CC in advance to fix the position of the DL CC. The position ofused bits is fixed according to the number of monitored/active CCspreviously determined between a base station and a user equipment. Whenthe user equipment transmits one ACK/NACK for a specific DL CC at thefixed bit position, the user equipment uses only one bit from among twobits allocated to the corresponding CC and transmits NACK (or ACK, orthe same value as the other 1-bit information) for the other one bit. Ifone DL CC requires two ACK/NACKs, the ACK/NACKs are mapped to twoallocated bits and transmitted. If ACK/NACK transmission is not requiredfor a specific DL CC, a value corresponding to NACK is transmittedunconditionally for the bit position corresponding to the DL CC. In thiscase, the base station can perform a re-transmission mode through NACKreception for a missing part in the corresponding DL CC due to PDCCHerror.

Referring to FIG. 12 , the user equipment generates containers fortransmitting the plurality of ACK/NACK information in due orderdepending on downlink component carrier index when generating payloadusing PUCCH format 2. In this case, if a plurality of transport blocksare received through at least one downlink component carrier among theplurality of downlink component carriers, containers for containingACK/NACK information are generated in due order depending on the orderof transport blocks received through the at least one downlink componentcarrier. Even if separate MIMO mode is applied to each downlinkcomponent carrier, the user equipment generates containers forcontaining ACK/NACK information in due order depending on downlinkcomponent carrier index and the order of transport blocks.

However, the base station should signal the type of container forcontaining ACK/NACK information to the user equipment, and can usedynamic indication through PDCCH or semi-static indication through upperlayer, for example, RRC layer, as a signaling method.

As shown in FIG. 12 , ACK/NACK information is contained in some ofmaximum 13 bits, and the other remaining bits of 13 bits are not used.This is to use a channel coding scheme of the related art as a channelcoding scheme for transmitting A/N information using the PUCCH format 2of the present invention. Accordingly, the channel coding scheme of thePUCCH format 2 uses a (20, A) block coding scheme. Also, even if aplurality of kinds of ACK/NACK information is transmitted using thePUCCH format 2, QPSK is used as the modulation scheme, whereby thechannel coding scheme of the related art can be used.

Meanwhile, as a channel coding scheme for transmitting a plurality ofkinds of ACK/NACK information using PUCCH format 2, a simple repetitioncoding scheme may be used instead of the (20, A) block coding scheme. Inthis case, after repeated coding for each of ACK/NACK information, theACK/NACK information may be contained in the container and then mappedinto the PUCCH format 2. Alternatively, after the ACK/NACK informationis contained in the container, repeated coding may be performed for theACK/NACK information and then mapped into the PUCCH format 2.

Meanwhile, scheduling information of downlink data transmission istransmitted through the PDCCH. If the PDCCH is transmitted using jointcoding, since scheduling grant of all downlink component carriers istransmitted using one payload, a problem that scheduling information ofa random downlink component carrier is not received does not occur.However, if the PDCCH is transmitted by containing schedulinginformation for each component carrier using separate coding, a problemthat scheduling grant of a random component carrier is not received mayoccur. In this case, DTX occurs in ACK/NACK transmission for datatransmission of the corresponding component carrier. Accordingly, ifscheduling grant is transmitted using separate coding, DTX as well asACK/NACK corresponding to data transmission associated with schedulinggrant which is not received should be considered. Hereinafter, a methodfor transmitting ACK/NACK information including DTX to PUCCH format 2will be described.

Examples of a method for feeding DTX back include a method forexplicitly transmitting ACK/NACK/DTX of each downlink component carrierand a method for transmitting ACK/NACK/DTX by mapping several states ofACK/NACK/DTX, which may occur in a plurality of downlink componentcarriers, into bit index. Each method is divided into non-MIMOtransmission (single TB) and MIMO transmission (multiple TB, SM).

First of all, the method for explicitly transmitting ACK/NACK/DTX ofeach downlink component carrier will be described.

If the base station does not perform MIMO transmission, i.e., for onetransport block transmitted from each downlink component carrier, threestates of ACK/NACK/DTX occur. In this case, in order to express threestates for each component carrier, 2 bits are required. Accordingly, inorder to indicate each of ACK/NACK/DTX information of each componentcarrier, (2×Ncc) bits are required. In other words, if the number ofmaximum component carriers is five, maximum 10 bits are transmittedthrough payload of PUCCH format 2. FIG. 13 is a diagram illustrating amethod for transmitting a plurality of kinds of ACK/NACK/DTX informationto payload of PUCCH format 2 in accordance with one embodiment of thepresent invention.

Unlike FIG. 13 , a method for coding and mapping ACK/NACK/DTXinformation corresponding to transport blocks transmitted through eachcomponent carrier into OFDM symbols may be provided. In other words, 2bits required to express ACK/NACK/DTX information for each componentcarrier can be transmitted to the message part of FIG. 10 by using theQPSK modulation scheme.

If the base station performs MIMO transmission, to express ACK/NACK/DTXinformation for a plurality of transport blocks transmitted from eachdownlink component carrier, one state of ACK/NACK and DTX for eachtransport block exists. In the LTE system, since two transport blocksare transmitted from one component carrier, a total of five statesoccur. To express these states, 3 bits are required. In order toindicate ACK/NACK/DTX information for each downlink component carrier,(3×Ncc) bits are required. In other words, if the number of maximumdownlink component carriers is five, maximum 15 bits are divided intofive parts of 3 bits each and then should be transmitted through payloadof PUCCH format 2. However, since size of payload that can betransmitted using PUCCH format 2 is maximum 13 bits as described above,the base station can transmit maximum 13 bits only in case of MIMOtransmission.

Accordingly, if the number of downlink component carriers is less than4, ACK/NACK/DTX information for each downlink component carrier isdivided like that the base station does not perform MIMO transmission.FIG. 14 is a diagram illustrating a method for transmitting ACK/NACK/DTXinformation in accordance with one embodiment of the present inventionwhen a base station is operated in a MIMO mode and the number ofdownlink component carriers is less than 4.

Although ACK/NACK/DTX information of each downlink component carrier ismapped into payload of PUCCH format 2 in FIG. 14 , a method for codingand modulating ACK/NACK/DTX information corresponding to transportblocks transmitted through each downlink component carrier and mappingthe ACK/NACK/DTX information into OFDM symbols may be used. In otherwords, 3 bits required to express ACK/NACK/DTX information for eachdownlink component carrier can be transmitted to the message part ofFIG. 10 by using the 8PSK modulation scheme.

If the number of downlink component carriers is five or more, PUCCHformat 2b is used. FIG. 15 is a diagram illustrating a method fortransmitting ACK/NACK/DTX information in accordance with one embodimentof the present invention when a base station is operated in a MIMO modeand the number of downlink component carriers is more than 5.

Referring to FIG. 15 , ACK/NACK/DTX information corresponding to fourcomponent carriers use CQI payload as illustrated in FIG. 14 , and 1 bitof 3 bits for expressing ACK/NACK/DTX information corresponding to thelast component carrier is allocated to the other 1 bit of CQI payload,and 2 bits for transmitting ACK/NACK from PUCCH format 2b are used.

Meanwhile, in the LTE-A system, a transmission mode for each downlinkcomponent carrier can be defined. Accordingly, bits for transmittingACK/NACK/DTX information can be defined for each component carrier. FIG.16 is a diagram illustrating a method for transmitting ACK/NACK/DTXinformation in accordance with one embodiment of the present inventionif a base station varies MIMO transmission for each downlink componentcarrier. In particular, FIG. 16 illustrates that component carriers 1and 3 are operated in a Non-MIMO mode and the other component carriersare operated in a MIMO mode.

Next, the method for transmitting ACK/NACK/DTX by mapping several statesof ACK/NACK/DTX, which may occur in a plurality of downlink componentcarriers, into bit index will be described.

First of all, if the base station does not perform MIMO transmission,3{circumflex over ( )}Ncc number of states may occur as ACK/NACK/DTXinformation. The number of states that can occur depending on the numberof component carriers and bits required to express the states areillustrated in Table 8 below. Also, Table 9 illustrates an example ofACK/NACK/DTX information expressed depending on the above method.

TABLE 8 # of ACK/NACK/DTX status combination (A, B, C)*, where A, B, Cin {ACK, NACK, DTX} and * means # of # of multiplicative combinationextension bits DL CCs Note: the order of A, B, C may be varied required1 3 2 2 9 4 3 27 5 4 81 7 5 243 8

TABLE 9 A/N/DTX state # of Note: if the number of DL CCs is more than 1,each Bit DL row of this cell represents A/N/DTX state of each DLrepresen- CCs CC tation 1 ACK 00 NACK 01 DTX 10 None (or reserved) 11 2ACK ACK 0000 ACK NACK 0001 ACK DTX 0010 NACK ACK 0011 NACK NACK 0100NACK DTX 0101 DTX ACK 0110 DTX NACK 0111 DTX DTX 1000 None (or reserved)1001 None (or reserved) 1010 None (or reserved) 1011 None (or reserved)1100 None (or reserved) 1101 None (or reserved) 1110 None (or reserved)1111 3 ACK ACK ACK 00000 ACK ACK NACK 00001 ACK ACK DTX 00010 ACK NACKACK 00011 ACK NACK NACK 00100 ACK NACK DTX 00101 ACK DTX ACK 00110 ACKDTX NACK 00111 ACK DTX DTX 01000 NACK ACK ACK 01001 NACK ACK NACK 01010NACK ACK DTX 01011 NACK NACK ACK 01100 NACK NACK NACK 01101 NACK NACKDTX 01110 NACK DTX ACK 01111 NACK DTX NACK 10000 NACK DTX DTX 10001 DTXACK ACK 10010 DTX ACK NACK 10011 DTX ACK DTX 10100 DTX NACK ACK 10101DTX NACK NACK 10110 DTX NACK DTX 10111 DTX DTX ACK 11000 DTX DTX NACK11001 DTX DTX DTX 11010 None (or reserved) 11011 None (or reserved)11100 None (or reserved) 11101 None (or reserved) 11110 None (orreserved) 11111

Although the number of component carriers is 3 in Table 9, even if thenumber of component carriers is 4 or more, extension can be performed inthe same manner as Table 9. Meanwhile, these bit indexes can betransmitted through payload of PUCCH format 2. In this case, the samescheme as that of the related art in which CQI is transmitted can beused as a channel coding and modulation scheme.

If the base station performs MIMO transmission, 5{circumflex over( )}Ncc number of states may occur. The number of states that can occurdepending on the number of component carriers and bits required toexpress the states are illustrated in Table 10 below. Also, Table 11illustrates an example of ACK/NACK/DTX information expressed dependingon the above method.

TABLE 10 # of ACK/NACK/DTX status combination (A, B, C, D, E)*, where A,B, C in {ACK, NACK, ACK, NACK, DTX} and * means # of # of multiplicativecombination extension bits DL CCs Note: the order of A, B, C may bevaried required 1 5 3 2 25 5 3 125 7 4 625 10 5 3125 12

TABLE 11 # of Bit DL CCs A/N/DTX state representation 1 TB 1 TB 2 ACKACK 000 ACK NACK 001 NACK ACK 010 NACK NACK 011 DTX 100 None (orreserved) 101 None (or reserved) 110 None (or reserved) 111 2 DL CC 1 DLCC 2 TB 1 TB 2 TB 1 TB 2 ACK ACK ACK ACK 00000 ACK ACK ACK NACK 00001ACK ACK NACK ACK 00010 ACK ACK NACK NACK 00011 ACK NACK ACK ACK 00100ACK NACK ACK NACK 00101 ACK NACK NACK ACK 00110 ACK NACK NACK NACK 00111NACK ACK ACK ACK 01000 NACK ACK ACK NACK 01001 NACK ACK NACK ACK 01010NACK ACK NACK NACK 01011 NACK NACK ACK ACK 01100 NACK NACK ACK NACK01101 NACK NACK NACK ACK 01110 NACK NACK NACK NACK 01111 ACK ACK DTX10000 ACK NACK DTX 10001 NACK ACK DTX 10010 NACK NACK DTX 10011 DTX ACKACK 10100 DTX ACK NACK 10101 DTX NACK ACK 10110 DTX NACK NACK 10111 DTX11000 None (or reserved) 11001 None (or reserved) 11010 None (orreserved) 11011 None (or reserved) 11100 None (or reserved) 11101 None(or reserved) 11110 None (or reserved) 11111

Likewise, although the number of component carriers is 2 in Table 11,even if the number of component carriers is 3 or more, extension can beperformed in the same manner as Table 11. Meanwhile, these bit indexescan be transmitted through payload of PUCCH format 2. In this case, thesame scheme as that of the related art in which CQI is transmitted canbe used as a channel coding and modulation scheme.

Meanwhile, a transmission mode may be defined for each componentcarrier. In this case, ACK/NACK/DTX information that can occur for eachcomponent carrier can become three states or five states. These twotypes of states may be used together, or the three states may be addedto the five states.

For example, if all downlink component carriers use non-MIMOtransmission mode, transmission is performed depending on definition ofTable 9. If any one or more downlink component carriers are defined in aMIMO transmission mode, bit index mapping of all downlink componentcarriers is defined depending on Table 11. In this case, in case ofnon-MIMO transmission mode, for mapping, three states should beconverted to five states. In this case, conversion can be performed insuch a manner as DTX→DTX, ACK→ACK/ACK and NACK→NACK/NACK.

Unlike this, since a transmission mode and setup information of eachdownlink component carrier can be sued by the user equipment, the methodfor transmitting ACK/NACK/DTX by performing bit index mapping for eachdownlink component carrier and performing joint coding may beconsidered.

Hereinafter, a method for allocating resources when ACK/NACK informationis transmitted using PUCCH format 2 will be described. First of all, thebase station can directly indicate whether to use PUCCH format 2 forACK/NACK information transmission through upper layer, for example, RRClayer.

Alternatively, the base station may indirectly indicate information ofdedicated resource allocation for PUCCH format 2 through RRC layer. Forexample, the base station may indicate that PUCCH format 2 can be usedin a specific component carrier, or may forward a value designatinglocation of dedicated resource used by PUCCH format 2 or a parameterrelated to the value. The other resources mapped into PUCCH format 2 andPUCCH format 1 of the LTE system can be used as the PUCCH format 2dedicated resources for ACK/NACK information transmission within anuplink component carrier.

FIG. 17 is a diagram illustrating a method for allocating PUCCH format 2dedicated resources according to one embodiment of the presentinvention. As shown in FIG. 17 , in LTE Rel-8 PUCCH, PUCCH format 2 thattransmits CQI is located at the edge of RB, PUCCH format 2a or PUCCHformat 2b that transmits CQI+ACK/NACK is located next to the edge, andACK/NACK is mapped into the PUCCH format 2a or the PUCCH format 2b. Forcompatibility with the related art system, PUCCH format 2 for ACK/NACKtransmission of the present invention is transmitted to next part to aresource to which Rel-8 PUCCH is transmitted.

Meanwhile, if there is resource allocated for LTE-A, PUCCH format 2 forACK/NACK transmission may be transmitted from the corresponding partonly. FIG. 18 is a diagram illustrating an example of using a PUCCHformat 2 dedicated resource allocated as a resource for LTE-A inaccordance with one embodiment of the present invention.

Also, PUCCH format 2 for existing CQI resource may be used again insteadof allocating the dedicated resource. In this case, a PUCCH allocationscheme for transmitting CQI or CQI+ACK/NACK can be used.

Hereinafter, another method for transmitting ACK/NACK information willbe described.

FIG. 19 is a diagram illustrating another method for transmittingACK/NACK information in accordance with one embodiment of the presentinvention. In particular, unlike FIG. 10 or FIG. 11 , FIG. 19illustrates that message pairing is not applied.

Referring to FIG. 19 , each OFDM symbol can be used to transmit ACK/NACKinformation of one component carrier. OFDM symbols for reference signaltransmission will be excluded.

In case of normal CP, since two OFDM symbols (S2 and S6) per slot areused as reference symbols, the other OFDM symbols can be used datasymbols for transmitting ACK/NACK information. If one reference symbolper slot is used, S4 can be used as a reference symbol and the other sixdata symbols can be used to transmit ACK/NACK information.

In case of extended CP, two reference symbols per slot may be used, orone reference symbol per slot may be used. Likewise, the other datasymbols except for the reference symbols can be used to transmitACK/NACK information.

Each of the symbols for transmitting ACK/NACK information can be used asa PUCCH corresponding to one downlink component carrier. For example,when the user equipment should transmit ACK/NACK signals of N number ofdownlink component carriers, the user equipment can map downlinkcomponent carriers in due order by starting from S1. For example, it isassumed that ACK/NACK signals for five downlink component carriers aretransmitted. In case of normal CP, the user equipment can map ACK/NACKsignal of each downlink component carrier into five data symbols of thefirst slot.

If the number of downlink component carriers for ACK/NACK informationtransmission is more than the number of data symbols that can betransmitted from one slot, symbols from a neighboring slot can be usedadditionally as much as wanted symbols regardless of hopping.

In this case, one data symbol transmits ACK/NACK information of onecomponent carrier through a specific modulation scheme (BPSK, QPSK,8PSK, or 16QAM). The data symbols may be mapped in due order dependingon component carrier indexes or in a type of constant offset.

In one subframe, remaining data symbols, i.e., data symbols, which havebeen used during the first ACK/NACK signal transmission, can repeatedlybe allocated to ACK/NACK information. The mapping order of data symbolsand the mapping order of ACK/NACK information can be varied. In thiscase, masking sequence such as Walsh code, DFT, ZC sequence, andm-sequence can be applied between the repeated symbols, wherebyspreading gain can be obtained.

Meanwhile, if repetition of ACK/NACK information of a specific componentcarrier is greater than repetition of ACK/NACK information of anothercomponent carrier, the ACK/NACK information repeated for the specificcomponent carrier can be subjected to truncation in due order which ispreviously defined.

The number of component carriers which should transmit ACK/NACKinformation can be defined depending on the number of component carriersspecified by the user equipment. However, how much ACK/NACK informationshould be transmitted can be notified directly by scheduling grant.Alternatively, the number of component carriers can be indicated througha specific control channel to indirectly indicate how much ACK/NACKinformation should be transmitted.

Some data symbols may not be used for repetition of ACK/NACK informationbut be used to mean the state (DTX) where a control signal is notreceived. At this time, the last symbol location of the second slot canfirst be selected as the location of DTX by considering location of asounding reference signal. Alternatively, DTX may be expressed in a typewhere symbol is not transmitted.

An example of another method for transmitting ACK/NACK informationaccording to the aforementioned embodiment of the present invention willbe described in detail. First of all, it is assumed that the basestation transmits transport blocks using five downlink componentcarriers.

FIG. 20 is a diagram illustrating an example of transmitting ACK/NACKinformation according to one embodiment of the present invention in caseof normal CP. In FIG. 20 , d0 to d4 correspond to numbers of downlinkcomponent carriers. Namely, it means that ACK/NACK information ofdownlink component carrier #0 is d0, and ACK/NACK information ofdownlink component carrier #1 is d1.

At this time, BPSK or QPSK can be applied to d0 to d4. Modulationschemes applied to ACK/NACK information are independent from eachanother. Namely, BPSK may be applied to d0˜d1 while QPSK may be appliedto d2˜d4.

Likewise, FIG. 21 is a diagram illustrating an example of transmittingACK/NACK information according to one embodiment of the presentinvention in case of extended CP.

Also, ACK/NACK information of a specific downlink component carrier canonly be repeated. FIG. 22 is a diagram illustrating a case whereACK/NACK information of a specific downlink component carrier isrepeated.

Referring to FIG. 22 , if the number of downlink component carriers isfour (DL CC #0˜3), ACK/NACK information of DL CC #3 can be repeated. Inthis case, it is preferable that the repeated ACK/NACK information d3 ofDL CC #3 represents DTX.

The DTX can be expressed depending on transmission of corresponding datasymbols. For example, if data symbols corresponding to a correspondingdownlink component carrier are transmitted, it means that ACK/NACK istransmitted. If the data symbols are not transmitted, it can be set thatDTX is transmitted.

FIG. 23 is a diagram illustrating a base station and a user equipmentthat can be applied to the embodiment of the present invention.

Referring to FIG. 23 , the wireless communication system includes a basestation (BS) 2310 and a user equipment (UE) 2320. In the downlink, thetransmitter is a part of the base station 2310 and the receiver is apart of the user equipment 2320. In the uplink, the transmitter is apart of the user equipment 2320 and the receiver is a part of the basestation 2310.

The base station 2310 includes a processor 2312, a memory 2314, and aradio frequency (RF) unit 2316. The processor 2312 can be configured toimplement procedures and/or methods suggested in the present invention.The memory 2314 is connected with the processor 2312 and stores variouskinds of information related to the operation of the processor 2312. TheRF unit 2316 is connected with the processor 2312 and transmits and/orreceives a radio signal. Namely, the RF unit 2316 includes atransmitting module and receiving module.

The user equipment 2320 includes a processor 2322, a memory 2324, and aradio frequency (RF) unit 2326. The processor 2322 can be configured toimplement procedures and/or methods suggested in the present invention.The memory 2324 is connected with the processor 2322 and stores variouskinds of information related to the operation of the processor 2322. TheRF unit 2326 is connected with the processor 2322 and transmits and/orreceives a radio signal. Namely, the RF unit 2326 includes atransmitting module and receiving module.

The base station 2310 and/or the user equipment 2320 can have a singleantenna or multiple antennas.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predetermined type.Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

The embodiments of the present invention have been described based onthe data transmission and reception between the base station and theuser equipment. A specific operation which has been described as beingperformed by the base station may be performed by an upper node of thebase station as the case may be. In other words, it will be apparentthat various operations performed for communication with the userequipment in the network which includes a plurality of network nodesalong with the base station can be performed by the base station ornetwork nodes other than the base station. The base station may bereplaced with terms such as a fixed station, Node B, eNode B (eNB), andaccess point. Also, the user equipment may be replaced with terms suchas mobile station (MS) and mobile subscriber station (MSS).

The embodiments according to the present invention can be implemented byvarious means, for example, hardware, firmware, software, or theircombination. If the embodiment according to the present invention isimplemented by hardware, the embodiment of the present invention can beimplemented by one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, microcontrollers,microprocessors, etc.

If the embodiment according to the present invention is implemented byfirmware or software, the embodiment of the present invention may beimplemented by a type of a module, a procedure, or a function, whichperforms functions or operations described as above. A software code maybe stored in a memory unit and then may be driven by a processor. Thememory unit may be located inside or outside the processor to transmitand receive data to and from the processor through various means whichare well known.

It will be apparent to those skilled in the art that the presentinvention can be embodied in other specific forms without departing fromthe spirit and essential characteristics of the invention. Thus, theabove embodiments are to be considered in all respects as illustrativeand not restrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims and all change whichcomes within the equivalent scope of the invention are included in thescope of the invention.

The present invention can be applied to a wireless communication system.More specifically, the present invention can be applied to a method andapparatus for transmitting ACK/NACK information in a wirelesscommunication system to which carrier aggregation is applied.

What is claimed is:
 1. A user equipment (UE) for generating anAcknowledgement/Negative Acknowledgement (ACK/NACK) payload in awireless communication system, the UE comprising: at least onetransceiver; at least one processor; and at least one computer memoryoperably connectable to the at least one processor and storinginstructions that, when executed by the at least one processor, performoperations comprising: receiving at least one transport block (TB) forat least one carrier among a plurality of carriers; and generating theACK/NACK payload based on receiving the at least one TB, wherein theACK/NACK payload comprises ACK/NACK bits for the plurality of carriers,wherein a total number of the ACK/NACK bits is determined at least basedon (i) a total number of the plurality of carriers, and (ii) for eachcarrier in the plurality of carriers, a respective maximum number of TBsthat the UE is configured to receive in a downlink frequency band of thecarrier, wherein for each of at least one first carrier among theplurality of carriers, the respective maximum number of TBs that the UEis configured to receive in a downlink frequency band of the firstcarrier is equal to 1, wherein for each of at least one second carrieramong the plurality of carriers, the respective maximum number of TBsthat the UE is configured to receive in a downlink frequency band of thesecond carrier is equal to 2, wherein the ACK/NACK bits comprise atleast: one ACK/NACK bit for each of the at least one first carrier; andtwo ACK/NACK bits for each of the at least one second carrier, andwherein the ACK/NACK payload comprises the ACK/NACK bits such that anACK/NACK bit associated with a carrier with a lower carrier indexprecedes an ACK/NACK bit associated with a carrier with a higher carrierindex in the ACK/NACK payload.
 2. The UE of claim 1, wherein theACK/NACK payload comprises the ACK/NACK bits such that, among the twoACK/NACK bits for each of the at least one second carrier, an ACK/NACKbit associated with a first TB precedes an ACK/NACK bit associated witha second TB in the ACK/NACK payload.
 3. The UE of claim 2, wherein theoperations further comprise: transmitting the ACK/NACK payload through aphysical uplink control channel (PUCCH) of an uplink carrier.
 4. The UEof claim 1, wherein based on only one ACK/NACK to be transmitted for adownlink frequency band of the at least one second carrier, the ACK/NACKpayload comprises the ACK/NACK bits such that one bit among two bits forthe downlink frequency band of the at least one second carrier is usedfor the one ACK/NACK.
 5. The UE of claim 4, wherein the ACK/NACK payloadcomprises the ACK/NACK bits such that the other one bit among the twobits for the downlink frequency band of the at least one second carrierhas a NACK value.
 6. The UE of claim 1, wherein based on no ACK/NACK tobe transmitted for a downlink frequency band of a certain carrier, theACK/NACK payload comprises the ACK/NACK bits such that an ACK/NACK bitfor the downlink frequency band of the certain carrier has a NACK value.7. The UE of claim 1, wherein a position of a respective ACK/NACK bitfor each of the plurality of carriers is fixed in the ACK/NACK payload.8. The UE of claim 1, wherein the total number of the ACK/NACK bits isgreater than the total number of the plurality of carriers.
 9. A basestation (BS) for receiving an Acknowledgement/Negative Acknowledgement(ACK/NACK) payload in a wireless communication system, the BScomprising: at least one transceiver; at least one processor; and atleast one computer memory operably connectable to the at least oneprocessor and storing instructions that, when executed by the at leastone processor, perform operations comprising: transmitting at least onetransport block (TB) for at least one carrier among a plurality ofcarriers for a user equipment (UE); and receiving the ACK/NACK payloadbased on transmitting the at least one TB, wherein the ACK/NACK payloadcomprises ACK/NACK bits for the plurality of carriers, wherein a totalnumber of the ACK/NACK bits is determined at least based on (i) a totalnumber of the plurality of carriers, and (ii) for each carrier in theplurality of carriers, a respective maximum number of TBs to betransmitted for the UE in a downlink frequency band of the carrier,wherein for each of at least one first carrier among the plurality ofcarriers, the respective maximum number of TBs to be transmitted for theUE in a downlink frequency band of the first carrier is equal to 1,wherein for each of at least one second carrier among the plurality ofcarriers, the respective maximum number of TBs to be transmitted for theUE in a downlink frequency band of the second carrier is equal to 2,wherein the ACK/NACK bits comprise at least: one ACK/NACK bit for eachof the at least one first carrier; and two ACK/NACK bits for each of theat least one second carrier, and wherein the ACK/NACK payload comprisesthe ACK/NACK bits such that an ACK/NACK bit associated with a carrierwith a lower carrier index precedes an ACK/NACK bit associated with acarrier with a higher carrier index in the ACK/NACK payload.
 10. The BSof claim 9, wherein the ACK/NACK payload comprises the ACK/NACK bitssuch that, among the two ACK/NACK bits for each of the at least onesecond carrier, an ACK/NACK bit associated with a first TB precedes anACK/NACK bit associated with a second TB in the ACK/NACK payload. 11.The BS of claim 9, further comprising: receiving the ACK/NACK payloadthrough a physical uplink control channel (PUCCH) of an uplink carrier.12. The BS of claim 9, wherein the total number of the ACK/NACK bits isgreater than the total number of the plurality of carriers.
 13. Anon-transitory computer readable storage medium storing instructionsthat, when executed by at least one processor, perform operationscomprising: receiving at least one transport block (TB) for at least onecarrier among a plurality of carriers; and generating anAcknowledgement/Negative Acknowledgement (ACK/NACK) payload based onreceiving the at least one TB, wherein the ACK/NACK payload comprisesACK/NACK bits for the plurality of carriers, wherein a total number ofthe ACK/NACK bits is determined at least based on (i) a total number ofthe plurality of carriers, and (ii) for each carrier in the plurality ofcarriers, a respective maximum number of TBs that a user equipment (UE)is configured to receive in a downlink frequency band of the carrier,wherein for each of at least one first carrier among the plurality ofcarriers, the respective maximum number of TBs that the UE is configuredto receive in a downlink frequency band of the first carrier is equal to1, wherein for each of at least one second carrier among the pluralityof carriers, the respective maximum number of TBs that the UE isconfigured to receive in a downlink frequency band of the second carrieris equal to 2, wherein the ACK/NACK bits comprise at least: one ACK/NACKbit for each of the at least one first carrier; and two ACK/NACK bitsfor each of the at least one second carrier, and wherein the ACK/NACKpayload comprises the ACK/NACK bits such that an ACK/NACK bit associatedwith a carrier with a lower carrier index precedes an ACK/NACK bitassociated with a carrier with a higher carrier index in the ACK/NACKpayload.
 14. The non-transitory computer readable storage medium ofclaim 13, wherein the ACK/NACK payload comprises the ACK/NACK bits suchthat, among the two ACK/NACK bits for each of the at least one secondcarrier, an ACK/NACK bit associated with a first TB precedes an ACK/NACKbit associated with a second TB in the ACK/NACK payload.
 15. Thenon-transitory computer readable storage medium of claim 14, wherein theoperations further comprise: transmitting the ACK/NACK payload through aphysical uplink control channel (PUCCH) of an uplink carrier.
 16. Thenon-transitory computer readable storage medium of claim 13, whereinbased on only one ACK/NACK to be transmitted for a downlink frequencyband of the at least one second carrier, the ACK/NACK payload comprisesthe ACK/NACK bits such that one bit among two bits for the downlinkfrequency band of the at least one second carrier is used for the oneACK/NACK.
 17. The non-transitory computer readable storage medium ofclaim 16, wherein the ACK/NACK payload comprises the ACK/NACK bits suchthat the other one bit among the two bits for the downlink frequencyband of the at least one second carrier has a NACK value.
 18. Thenon-transitory computer readable storage medium of claim 13, whereinbased on no ACK/NACK to be transmitted for a downlink frequency band ofa certain carrier, the ACK/NACK payload comprises the ACK/NACK bits suchthat an ACK/NACK bit for the downlink frequency band of the certaincarrier has a NACK value.
 19. The non-transitory computer readablestorage medium of claim 13, wherein a position of a respective ACK/NACKbit for each of the plurality of carriers is fixed in the ACK/NACKpayload.
 20. The non-transitory computer readable storage medium ofclaim 13, wherein the total number of the ACK/NACK bits is greater thanthe total number of the plurality of carriers.